There are only 4 years from 1970 forward that have
DDO's on dimes. The 1970,71,72-S mints and 1989-P. Those for dates and mintmarks are the only ones forward till this year that none of the other years have a
DDO. So on these dimes, I'd forget checking theses obverses. A few years on the current years has
DDR's.
Check which ones on V.V to see what years they are and what they look like.